Radio receiver



F. KREIENFELD RADIO RECEIVER May so, 1939.

Filed July 25, 1956 R Y 0M E l N N E g R ER 0 W w Am m RB Patented May 30, 1939 UNITE s'mr RADIO RECEIVER Friedrich Kreienfeld, Berlin, Germany, assignor to 'I'elefunken Gesellschaft fiir Drahtlose Telegraphic in. b. 11., Berlin, Germany, a corporation of Germany Application July 25, 1936, Serial No. 92,517 In Germany July 31, 1935 3 Claims.

The present invention relates broadlyto multirange' coupling arrangements, and more particularly, to improvements in multi-range circuits incorporating Wave traps in the antenna lead-in for the purpose of preventing interference from powerful transmitters.

It has been found that when Wave traps are incorporated as mentioned above, the tuning of the receiver may be affected. Accordingly, it is an object of the present invention to devise a circuit arrangement which overcomes this disadvantage.

The single figure of the drawing illustrates schematically a circuit arrangement incorporating the invention.

In the drawing, numeral l represents the antenna and numeral 2 the first tube of a receiver or amplifier connected to the antenna. The input circuit 3 between the grid and cathode of tube 2 comprises a variable condenser the intermediate coil 5 and the series coil 6. Across the latter coil there is bridged a switch 1 which,

upon operation, short-circuits coil 6 whenever' it is desired to receive the intermediate Wave range. Coils 8 and 9 placed in the antenna circuit are coupled to the coils 5 and B respectively. The free end of coil 8 is grouded while the free end of coil 9 is connected to the antenna across the blocking circuits or wave traps Iii and H. Adjacent ends of the coils 8 and 9 are connected together and may at times be connected through switch 12 to a point intermediate the blocking or tank circuits iii and H previously mentioned. These blocking circuits comprise variable condensers and coils, the latter being provided with a plurality of tapped points.

Normally, when receiving on the intermediate wave range, the long wave antenna coil 9 is bridged by the switch I2. In the absence of blocking circuits, the natural wave of the antenna circuit is approximately 200 m thus lying, as regards frequency, at the upper end of the one wave range, which may correspond to the broadcasting wave range. Now, by providing a blocking circuit, a self inductance acting as a wave expansion coil is placed in series With the antenna, thus shifting the natural wave of the antenna towards the inside of the wave range and thereby assuming a value approximately equal to 300 m. Hence, at this frequency, the tuned input circuit 3 is coupled to an antenna circuit that is also tuned, so that coupling waves and frequency displacements occur making it very difiicult at any rate to provide tuning to such frequency. i

To avoid these difficulties, it is proposed in accordance with the invention to bridge the long wave blocking and to associate the long wave blocking circuit I0 With the long wave coupling coil 9 in such a manner that a single switch such as i2 may be used to remove both from the circuit when closed and connect both to the circuit when open.

When closed the switch l2 therefore besides the coupling coil 8, only the short wave blocking circuit l! is inserted for receiving on the intermediate wave range. Hence, the blocking circuit either lengthens or shortens the antenna in accordance with its tuning position relative to the receiving Wave.

What is claimed is:

i. In a radio receiver, an antenna circuit comprising an energy collector, a series arrangement of tunable tank circuits, each tank circuit having a variable capacitor and a tapped inductance, said antenna being connectable with different ones, selectively, of the taps on one of said tank circuits, a transformer coupling arrangement having primary windings connectable with the other one of said tank circuits through a of the primary and secondary windings respectively, and means for at times establishing a short circuit between the first described tank circuit and an intermediate point on said primary windings.

2. In radio signaling apparatus, an electronic tube having a signal input circuit including at least two coupling coils, switching means for short-circuiting one of said coils, an antenna circuit including a plurality of tank circuits and at least two coupling coils, said last named coils being coupled respectively to the coils in said input circuit and switching means for short-circuiting one of said tank circuits and one of the coils in the antenna circuit.

3. In a radio receiving apparatus adapted for reception within Widely separated wave bands, an antenna circuit comprising an energy collector, a series arrangement of tuned tank circuits each tank circuit including a capacitor and an inductanca'said antenna being connected to one of said tank circuits, a transformer coupling arrangement having primary windings in series, one extremity of said primary windings being grounded, the other being connected to the other one of said tank circuits, an amplifier stage having an input circuit inclusive of secondary windings in said transformer coupling arrangement, means for short-circuiting portions of the primary and secondary windings respectively and a single means for short-circuiting one of the tank circuits and one of the primary windings.

FRIEDRICH KREIENFELD. m 

